Question 1062277
It helps to draw this.  From the drawing, the estimate is between 400 (they are the same direction) to 800, less than the distance either is from the city.
Law of cosines.
c^2=a^2+b^2-2abcos C
c^2=800^+1200^2-2(800)(1200)cos 30
=417231.22
c=sqrt (417231.22)=645.93 rounded to 646 miles.